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About sim908 interaction

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mohanpatil

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Hi Friends,
I know without sim908 we can not send AT COMMANDS but i want to interact by microcontroller of stm32f103ve and in my application board UART OF stm32f103ve is connected to UART of sim908 (pin15 and pin16) i tried to send the command by UART TX PIN OF stm32f103ve but the problem is the status of RESETING The flag of STM32F103ve is done by hardware so i could not reach upto sim908's RX PIN so help me i am very confused ,
Regards
Mohan::cry:
 

I don't have answer for your question but I have a doubt in interfacing SIM908 with microcontroller through UART.. I'm using MSP430 F5 series Microcontroller. Do i need MAX232 and use RS232 between the microcontroller and SIM908 for serial communication.. (It's said in the manual that no need for level transition to connect to CMOS devices)..

How to know whether to use RS232 or connect directly without any level transition?
-
DK
 

Actually if u are using microcontroller then there is no need to connect rs232 cable we can directly connect the rx and tx pins of Microcontroller and sim908 and can read reply of gsm from rx pin of mcu.
 
we can directly connect the rx and tx pins of Microcontroller and sim908 and can read reply of gsm from rx pin of mcu.
Click to expand...

The SIM908 Uart pins are at 2.8 volts so unless your mcu IO pins are at the same voltage you will need level shifting otherwise problem!

Cheers.
 
Last edited:
Hi Friends
Thanx for giving me support but now i dont know whether they are at same level but i am getting data from uart of sim908 still i am facing one problem data from gps is recieved in mode 0 that is AT+CGPSINF=0\r the reply is 0,0.000000,0.000000,0.000000,2................ LIKE wise data is getting means everytime i am getting longitude and lattitude 0.000000 as it is not proper . i also power on gps by sending AT+CGPSPWR=1\r AND AT+CGPSRST=0\r still some time getting proper but most of the time is improper please help me friend i am in very bad situation.....

Regards
Mohan patil
 

hello

In my project is using sim908. Are You send comand AT for GPS via pins 68 and 71 (68:GsmRXD 71:GsmTXD ) ?

if I have to use both UART of sim908 need a MCU with 2 UART

thanks for the help
 

Hello ,
Yes i send AT COMMANDS for gps vial pin 68 and 71




fighter_ar said:
hello

In my project is using sim908. Are You send comand AT for GPS via pins 68 and 71 (68:GsmRXD 71:GsmTXD ) ?

if I have to use both UART of sim908 need a MCU with 2 UART

thanks for the help
Click to expand...
 

mohanpatil said:
Hi Friends
Thanx for giving me support but now i dont know whether they are at same level but i am getting data from uart of sim908 still i am facing one problem data from gps is recieved in mode 0 that is AT+CGPSINF=0\r the reply is 0,0.000000,0.000000,0.000000,2................ LIKE wise data is getting means everytime i am getting longitude and lattitude 0.000000 as it is not proper . i also power on gps by sending AT+CGPSPWR=1\r AND AT+CGPSRST=0\r still some time getting proper but most of the time is improper please help me friend i am in very bad situation.....

Regards
Mohan patil
Click to expand...

Did you keep the GPS antenna in the open space or near window? It worked for me when i had the same problem..
 

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